This application relates to weather radar systems. More particularly, this application relates to the identification of hazardous and non-hazardous (e.g. stratiform verses convective) by weather radar systems.
Weather radar systems are known in the art for detecting and displaying severe weather to a crew in an aircraft on a two-dimensional map display showing range, bearing, and intensity of a detected weather system, which may be convective or stratiform in nature. Flight hazards due to weather conditions are primarily the result of precipitation and turbulence. Airborne weather radar systems have been optimized to detect rain or wet precipitation.
Although aircrews desire to use the weather radar system as a hazard detector, the weather radar system does not make direct estimates of hazard. Instead, the radar system remotely estimates the reflectivity of precipitation in a sampled volume of the atmosphere. A simple model of reflectivity verses precipitation rate can then be used to estimate the rate of precipitation in that atmospheric volume.
Historically, high precipitation rates and high radar reflectivity estimates have been associated with two different hazards produced by convective weather: hail and turbulence. However, precipitation is driven from several major weather categories including the categories of stratiform, convective, orthographic, frontal, etc., some which are not necessarily hazardous.
Radar systems are calibrated to produce a green display when any precipitation is detected, a yellow display where reflectivity is high enough to produce some chance of a hazard, and a red display when weather produces reflectivity estimates high enough to infer a weather hazard is very likely. The current hazard metric is radar reflectivity based upon the JT Lee Hazard Curves, where 20-29 dBz equals green, 30-39 dBz equals yellow and 40 dBz and greater is red.
The JT Lee Hazard Curves describe the increased probability of hazards with the increase in dBz levels in North America. The likelihood of weather hazards is based on statistics generated over the North American continent in the spring and summer from radar estimates reflectivities taken from ground based radars. However, reflectivity is not necessarily indicative of a hazardous weather condition throughout the world, only of rainfall rates. Airborne weathers radars that are used at other altitudes and geographies from where the hazard model data was captured do not necessarily capture the threat statistics desired by the aircrew.
Pilots are taught to stay away from hazardous weather. Pilots perceive weather encoded with either yellow or red levels as hazardous. Stratiform weather can exhibit yellow responses and still be non-hazardous. Also, convective weather that is at the end of its convective cycle can exhibit yellow responses and still be non-hazardous. Maneuvers around yellow encoded weather that is not hazardous results in an inefficient flight path.
The separation of weather situations into hazardous and non-hazardous conditions provides an operational advantage to aircrews. Planes flying through the tropical convergence zone (the equatorial regions) routinely encounter lines of storms tens of miles deep and hundreds of miles wide. A weather radar with the ability to differentiate hazardous weather conditions from non-hazardous weather conditions could provide aircrews with enough information to make a safe and smooth penetration, as opposed to a long flight path deviation, saving the airline time and money.
As aircraft traffic increases, conservative routing by air traffic control in the vicinity of bad weather becomes more difficult. Therefore, air traffic controllers require a greater ability to route airplanes through safer portions of hazardous weather.
Accordingly, there is a need for a system and method of identifying hazardous and non-hazardous weather. Further, there is a need for a system for and method of automatically adapting the display of rainfall rates to reflect the likelihood of hazards. Yet further, there is a need for an avionic weather radar system which can differentiate hazardous versus non-hazardous weather. Further still, there is a need for a weather radar system that can identify hazardous versus non-hazardous weather regions to enable more direct flights through weather.
It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the above-mentioned needs.